The invention described herein relates generally to gas shielding of heated areas and more particularly to structures for preventing oxidation by uniformly distributing inert shielding gas over the weld area of workpieces being welded together.
A significant problem in welding is that the weld material and the workpieces can oxidize in air when they are heated. If the weld oxidizes, it will be porous and weak. It is well known that welding in an atmosphere devoid of oxygen will prevent oxidation. Workpieces such as pipes have been welded together in an atmosphere of inert gas. The air within a sealed chamber is replaced with an inert gas and welding is performed inside the chamber. Using such a chamber is expensive, time-consuming and requires a large supply of inert gas.
To avoid these disadvantages, other devices for surrounding the weld area with an inert gas have been developed. These include a gas flooding device for attachment to a welding tool, disclosed in U.S. Pat. No. 3,875,364 to Boyett, and a flexible conduit with a porous wall through which inert gas is distributed, disclosed in U.S. Pat. No. 3,450,857 to Webb. Both of these devices provide an atmosphere of inert gas around a portion of the weld area during welding and for a limited period of time thereafter while the weld area cools. Neither device provides a uniform atmosphere of inert gas around the entire weld area of the workpieces throughout the welding operation. Consequently, the speed with which welding can be performed with these devices is limited by the cooling rate of the weld area and the extent to which the weld area is covered by inert gas. It is therefore desirable to cover the entire weld area with an uniform atmosphere of inert gas throughout the welding operation.